In applications of sound reinforcement equipment, a major problem that affects the gain of a sound reinforcement system is that the direct sound received by a microphone has the same frequency and same phase as the acoustic signals fed back by various reasons. It thus is easy to generate a positive feedback and cause howling in the sound reinforcement system.
The feedback acoustic wave and the acoustic wave ought to be received by the microphone are generally heading in different directions, so the most common approach to solve the above problem is to enhance the directional characteristic of the microphone to reduce the impact of the feedback acoustic wave.
The existing cardioids or super cardioids microphone is generally most sensitive to the acoustic wave input incoming the front, and is not sensitive to the acoustic wave incoming from the back, such that the feedback acoustic wave from the back can be inhibited, but sometimes the feedback acoustic wave incoming from above, below, left or right would also causes interference.
The “8” shaped direction microphone is generally sensitive to the acoustic wave incoming both from the front and back, and is not sensitive to the acoustic wave incoming from above, below, left or right. Thus, the feedback problem of the acoustic wave from back still can't be resolved.
In addition, the existing cardioids, super cardioids and “8” shaped direction microphone have different directional responses for acoustic waves with different frequencies.
There is always a stringent requirement for a single microphone to operate in a sound environment due to limitations of gain characteristic, directional characteristic, frequency response, and so on. It is often difficult to obtain a good result of sound pickup (sound transmitting) when the sound environment is relatively complex. For example, a decrease in output gain, distortion or howling could happen because of the far distance between a target sound source and a sound pickup (sound transmitting) device, a hard angle, a severe background noise or a strong feedback. Especially when the sound reinforcement equipment should be supported by a multitude of sound pickup (sound transmitting) devices, it is rather complex in regulation and adjustment. Thus, it becomes necessary to have a sound pickup (sound transmitting) device, which outputs a higher gain for a forward acoustic wave actuation, plays a greater inhibition role in oblique acoustic waves, and has a stable directivity, to simplify demands of the sound reinforcement equipment on environment, so as to meet the requirements of sound pickup (sound transmitting) in an environment with a stronger acoustic wave feedback and a higher environmental noise, achieve remote sound pickup (sound transmitting), simplify the device regulation and operation, and obtain a good result of sound reinforcement.